UPDATE 3: We should note that today makes for the second major Twitter blackout this past year. In June, the site was downed by a "a cascaded bug in one of our infrastructure components," according to a tweet from the company.

UPDATE 4: Twitter appears to be back up, for us at least. (As well as TechCrunch.) Both mobile and the normal web version are loading for us, and we were successfully able to tweet. According to the AP, the Twitter outage seemed to be worldwide, though it's difficult to say to what level different users were affected. Twitter being Twitter, already jokes are filtering in. "First, they came for Gchat, and I said nothing, because I couldn't. Then they came for Twitter...." The Atlantic's Matt O'Brien tweets.

UPDATE 5: At about 2 p.m. ET, Twitter issued an apology for the morning outage. The company explains:

The cause of today’s outage came from within our data centers. Data centers are designed to be redundant: when one system fails (as everything does at one time or another), a parallel system takes over. What was noteworthy about today’s outage was the coincidental failure of two parallel systems at nearly the same time.

So it wasn't because of high tweet volume from the Olympics. Phew. Because the problem would have only gotten worse with the opening ceremonies on Friday.